4 February 1994
In a massacre on 4 February 1994 Abbas al-Bager Abbas opened fire killing 20 praying muslims and wounding 33 others  in a mosque in Khartoum, Sudan. Abbas was eventually gunned down by police after he refused to surrender. It was generally thought that he acted alone though there were few eye witnesses who claimed to have seen at least three other men with him that night. Abbas belonged to the Islamic fundamentalist group Al-Takfir wa al-Hijran which had a long standing grudge against the Islamic sect Al- Sunna Al-mohammediyya  Mosque .  Police arrested 65 members of the sect after the massacre. The tension between the two sects was caused by differences of opinion regarding the implementation of the Sharia Law in government.
References

Murderpedia, Abbas Baqir ABBAS, from Murderpedia, [online], Available at murderpedia.org [Accessed: 18 January 2012]|BBC News Gunman kills 20 in Sudan mosque, from BBC, [online], Available at news.bbc.co.uk [Accessed: 18 January 2013]